Electrochemical/gas analysis systems are known having sensor units for specific analysis tests selectively installable in a multi-channel analysis system. Electrical connections are made between the individual sensor contacts and contacts on the analysis system.
Prior sensor electrode to analyzer system contacts were extremely delicate and required time-consuming and expensive hand assembly. Careless insertion or removal of sensors into these connectors could easily result in connector damage. In addition to low insertion-removal cycle lifespans, these connectors frequently provided less than optimal sensor to system signal reliability.
A major problem which prior art analysis systems fail to address is the ease with which front-end electronics with input impedances of several hundred million ohms can be damaged by electrostatic discharge (ESD) which occasionally occurs on insertion of static charged sensors. Some sensors have plastic bodies prone to static charge build-up, particularly when employed in low humidity environments. A charged sensor brought into contact with an analysis system contact can apply built-up potential to the high impedance, front-end electronics, thereby damaging them.
There is a need for simple and accurate diagnostic testing of analysis system electronics including high impedance front-end pre-amplifier circuitry and low impedance back-end signal processing circuitry.
In order to test these elements, one prior art gas analysis system provides a diagnostic tool which may be referred to as an electrode simulator. In this prior art analysis system, it is necessary to remove all of the sensors from the system when it is suspected that either a sensor or one channel of a multi-channel system is malfunctioning. The sensor simulator, which is battery powered, is installed in place of the sensors and is electrically connected to the sensor contacts to provide test signals to the analysis system through the same contacts that connect the front-end and back-end electronics.
Because all electrodes must be removed in order to install the electrode simulator, time is consumed and sensors which are not suspect are thereby subject to foreign matter introduction, damage or loss. Further, increased removal-insertion cycling decreases the life expectancy both of the sensor and system contacts. Finally, a discrete piece of test equipment such as the electrode simulator is expensive to manufacture in small quantities, requires separate maintenance, and must be located and transported to the analyzer system site by service personnel.
Another prior art approach to providing enhanced testing of an electrochemical/gas analyzer system involves providing reed relays to selectively insert a test signal to the high impedance front-end electronics in place of a sensor signal. Contact testing cannot be achieved and implementing reed relays requires additional space proximate the front-end electronics.